lucene/analysis/common/src/java/org/apache/lucene/analysis/shingle/ShingleAnalyzerWrapper.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package org.apache.lucene.analysis.shingle;

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.AnalyzerWrapper;
import org.apache.lucene.analysis.standard.StandardAnalyzer;

/**
 * A ShingleAnalyzerWrapper wraps a {@link ShingleFilter} around another {@link Analyzer}.
 *
 * <p>A shingle is another name for a token based n-gram.
 *
 * @since 3.1
 */
public final class ShingleAnalyzerWrapper extends AnalyzerWrapper {

  private final Analyzer delegate;
  private final int maxShingleSize;
  private final int minShingleSize;
  private final String tokenSeparator;
  private final boolean outputUnigrams;
  private final boolean outputUnigramsIfNoShingles;
  private final String fillerToken;

  public ShingleAnalyzerWrapper(Analyzer defaultAnalyzer) {
    this(defaultAnalyzer, ShingleFilter.DEFAULT_MAX_SHINGLE_SIZE);
  }

  public ShingleAnalyzerWrapper(Analyzer defaultAnalyzer, int maxShingleSize) {
    this(defaultAnalyzer, ShingleFilter.DEFAULT_MIN_SHINGLE_SIZE, maxShingleSize);
  }

  public ShingleAnalyzerWrapper(Analyzer defaultAnalyzer, int minShingleSize, int maxShingleSize) {
    this(
        defaultAnalyzer,
        minShingleSize,
        maxShingleSize,
        ShingleFilter.DEFAULT_TOKEN_SEPARATOR,
        true,
        false,
        ShingleFilter.DEFAULT_FILLER_TOKEN);
  }

  /**
   * Creates a new ShingleAnalyzerWrapper
   *
   * @param delegate Analyzer whose TokenStream is to be filtered
   * @param minShingleSize Min shingle (token ngram) size
   * @param maxShingleSize Max shingle size
   * @param tokenSeparator Used to separate input stream tokens in output shingles
   * @param outputUnigrams Whether or not the filter shall pass the original tokens to the output
   *     stream
   * @param outputUnigramsIfNoShingles Overrides the behavior of outputUnigrams==false for those
   *     times when no shingles are available (because there are fewer than minShingleSize tokens in
   *     the input stream)? Note that if outputUnigrams==true, then unigrams are always output,
   *     regardless of whether any shingles are available.
   * @param fillerToken filler token to use when positionIncrement is more than 1
   */
  public ShingleAnalyzerWrapper(
      Analyzer delegate,
      int minShingleSize,
      int maxShingleSize,
      String tokenSeparator,
      boolean outputUnigrams,
      boolean outputUnigramsIfNoShingles,
      String fillerToken) {
    super(delegate.getReuseStrategy());
    this.delegate = delegate;

    if (maxShingleSize < 2) {
      throw new IllegalArgumentException("Max shingle size must be >= 2");
    }
    this.maxShingleSize = maxShingleSize;

    if (minShingleSize < 2) {
      throw new IllegalArgumentException("Min shingle size must be >= 2");
    }
    if (minShingleSize > maxShingleSize) {
      throw new IllegalArgumentException("Min shingle size must be <= max shingle size");
    }
    this.minShingleSize = minShingleSize;

    this.tokenSeparator = (tokenSeparator == null ? "" : tokenSeparator);
    this.outputUnigrams = outputUnigrams;
    this.outputUnigramsIfNoShingles = outputUnigramsIfNoShingles;
    this.fillerToken = fillerToken;
  }

  /** Wraps {@link StandardAnalyzer}. */
  public ShingleAnalyzerWrapper() {
    this(ShingleFilter.DEFAULT_MIN_SHINGLE_SIZE, ShingleFilter.DEFAULT_MAX_SHINGLE_SIZE);
  }

  /** Wraps {@link StandardAnalyzer}. */
  public ShingleAnalyzerWrapper(int minShingleSize, int maxShingleSize) {
    this(new StandardAnalyzer(), minShingleSize, maxShingleSize);
  }

  /**
   * The max shingle (token ngram) size
   *
   * @return The max shingle (token ngram) size
   */
  public int getMaxShingleSize() {
    return maxShingleSize;
  }

  /**
   * The min shingle (token ngram) size
   *
   * @return The min shingle (token ngram) size
   */
  public int getMinShingleSize() {
    return minShingleSize;
  }

  public String getTokenSeparator() {
    return tokenSeparator;
  }

  public boolean isOutputUnigrams() {
    return outputUnigrams;
  }

  public boolean isOutputUnigramsIfNoShingles() {
    return outputUnigramsIfNoShingles;
  }

  public String getFillerToken() {
    return fillerToken;
  }

  @Override
  public final Analyzer getWrappedAnalyzer(String fieldName) {
    return delegate;
  }

  @Override
  protected TokenStreamComponents wrapComponents(
      String fieldName, TokenStreamComponents components) {
    ShingleFilter filter =
        new ShingleFilter(components.getTokenStream(), minShingleSize, maxShingleSize);
    filter.setMinShingleSize(minShingleSize);
    filter.setMaxShingleSize(maxShingleSize);
    filter.setTokenSeparator(tokenSeparator);
    filter.setOutputUnigrams(outputUnigrams);
    filter.setOutputUnigramsIfNoShingles(outputUnigramsIfNoShingles);
    filter.setFillerToken(fillerToken);
    return new TokenStreamComponents(components.getSource(), filter);
  }
}